As a typical and ordinary example of conventional heating device for seat, there has been provided a heating device, in which a heating matter comprising a heating wire (code-like heater) is controlled by thermostat to maintain a predetermined temperature. However, this type of temperature control by thermostat determines the temperature of heating matter according to the activating temperature of thermostat, and if a user wishes to set the temperature of seat heating device so that comfortable seating feeling may be obtained, a plurality of thermostats respectively having different activating temperatures should be arranged, or calorific value of supplementary heater for activating thermostat should be changed. This would require increased assembly parts and complex circuit structure, and it has been difficult to realize such a heating device.
Yet there has been an example of seat heating device coping with such a demand, as disclosed in FIGS. 8 to 10. With reference to FIGS. 8 to 10, there is a heating matter 104 in which a heating wire (cord-like heater) 103 has been arranged in a meandering shape on a base substance 102, and a temperature control circuit 101 is connected to the heating matter 104 in series outside the base substance 102. There is also a temperature detection element 105, comprising such as thermistor, placed at a position adjacent to the heating wire 103. The temperature signal outputted from the temperature detection element 105 controls a current control element such as Power MOS-FET (field effect transistor) incorporated in the temperature control circuit 101, whereby the temperature control of the heating matter 104 is carried out.
There is a circuit board (not shown) of the temperature control circuit 101 as discussed above, incorporated in a case body 113, comprising a first case body 111 and a second case body 112. The first case body 111 has an attachment part 114 serving for attaching and detaching the case body 113 to and from a seat. The second case body 112 has a circuit board fixed thereon.
The case body 113 has connectors 115 which electrically connect the heating matter 104 with the temperature control circuit 101, for the purpose of improving workability by solving problems of limited setting order while mounting the heating matter 104 to the seat.
The temperature detection element 105 has been fixed on the heating matter 104, and it is assumed that the temperature detection element 105 would be electrically connected to the temperature control circuit 101 via the connectors 115. On the other hand, there are lead wires 108 connected to any parts other than the heating matter 104 (for example, connected to a power supply unit), extending outside from a hole of the second case body 112 (for example, see Patent Document 1).
Apart from the Patent Document 1, there are many patent documents disclosing temperature control by using temperature detection element such as thermistor (for example, see Patent Document 2, etc).
With reference to the structure as shown in FIGS. 8 to 10, there are several patent documents suggesting structures in which the temperature control circuit 101 and the temperature detection element 105 have been fixed on the base substance 102 of the heating matter 104 (for example, see paragraphs 0003 and 0005 of Patent Document 3).    Patent Document 1: Japanese Unexamined Patent Publication (Tokukai) No. 2004-272755;    Patent Document 2: Japanese Unexamined Patent Publication (Tokuhyo) No. 2004-504082; and    Patent Document 3: Japanese Unexamined Patent Publication (Tokukai) No. 2004-217796.